Isolated by Arabs angry over the peace treaty with Israe, Egypt is waging a concerted diplomatic campaign for support in black Africa despite the lure of oil largess from the hard-line Arabs.

The effort, which includes a pledge by President Anwar Sadat to attend the Organization of African Unity summit meeting in Monrovia, Liberia, next month, is designed to strengthen Egypt against Arab attacks in OAU and other international forums such as the United Nations and the nonaligned movement.

The Egyptian effort was launched by a suggestion leaked to Cairo newspapers early this month that an all-African military force could monitor Israeli withdrawal in the Sinai if the mandate of U.N. forces there is not renewed because of a Soviet veto.

Diplomats here express skepticism that Israel would accept such a force. Egyptian officials say the suggestion has never been put to Israel directly so they are unable to gauge Israeli reaction. The Africans themselves are still discussing the suggestion, the officials add.

The issue is current because the mandate of the 4,000-man U.N. force in the Sinai comes up for renewal in the Security Council next month. There is fear the Soviet Union will protest the Egptian treaty with Israel.

If that happens, diplomats here expect the most likely response from the United States would be to create a multinational supervisory force outside the United Nations, perhaps including some Africans but not exclusively.

Whatever the fate of Egypt's suggestion, it underlines the effort to gather support in black African nations to counter anti-Egyptian moves by Arab Africans, particularly Alegeria and Libya. Even King Hassan of Morocco, traditionally a moderate friendy to Sadat, has joined the Arab boycott decided in March at Baghdad. Only Sudan, Somalia and Oman have stuck with Sadat.

Sadat dramatized his African card in a speech to the new parliament last week. He went out of his way to announce his intention to attend the OAU summit in Liberia and sernly emphasized his refusal to recognize the new Rhodesian government of Bishop Abel Muzorewa,

Following up Egyptian Deputy Foreign Minister Bouros Ghali called in African ambassadors in Cairo for a meeting - trumpeted in the Cairo press - to lay groundwork for the OAU proceedings. The idea, Egyptian officials say, was to head off in advance an expected effort by Libya and Algeria to exclude Egypt from the organization.

This is considered particularly crucial following Egzpt's exclusion from the Islamic Conference last month in Morocco and steps taken by Arab League members to expel Egypt and transfer league headquarters from Cairo, where it had stood since the group was founded in 1945, to Tunis.

In addition, Egyptian diplomats are seeking African support for a nonaligned movement meeting scheduled later this year in Havana. Egypt traditionally has played an important role in the movement.

Egyptian diplomats feel they already have scored a significant triumph in the nonaligned movement by preventing their Arab opponents from making censure of Egypt an item for consideration at Havana.